Diplomats from 109 countries today agreed to end their use of cluster bombs in eight years, following an announcement from Britain that it was to scrap its stockpiles of the weapons.

The prime minister, Gordon Brown, had earlier said he hoped the British move would "break the logjam" at the Dublin summit. He was praised by campaigners for a "major act of statesmanship".

The cluster bomb treaty, concluded earlier than expected, however excludes major producers and stockpilers of the weapons – including the United States, Russia and China.

Cluster weapons are highly controversial because they scatter small "bomblets" over a wide area. Many do not explode on impact and are activated later by civilians. They caused more than 200 civilian casualties in the year after the Lebanon ceasefire and more civilian casualties in Iraq in 2003 and Kosovo in 1999 than any other weapon system.

Earlier, Brown had said in Downing Street the decision to take British cluster bombs out of service would lead to agreement on the treaty. "I look forward to other countries following us in this action and I look forward to other countries being able to take these cluster bombs out of service," he said

"I think this would be a big step forward to make the world a safer place."

The British announcement ended a long-running Whitehall dispute, which pitted the Ministry of Defence against the Foreign Office and Department for International Development. The MoD says the number of cluster bombs in the armoury is "operationally sensitive" but concedes that decommissioning them will cost tens of millions of pounds.

Well-placed sources told the Guardian that the government would announce the ban despite opposition from the military.

The cluster munitions to be scrapped by Britain are the lsraeli-designed M85 artillery weapon – used during the 2003 invasion of Iraq and in attacks on Lebanon two years ago – and the M73, part of a weapons system for Apache helicopters.

While the government appears happy for British forces to get rid of their M85 weapons immediately, it wants a "phasing out period" for its M73s.

Potential problems arising from the treaty include the UK's ability to serve in coalition with countries - such as the United States - which oppose a ban.

Participants in the talks were last night embroiled in the vexed question of whether troops from countries who sign up to the ban could go on operations with those countries that do not.

Preventing them from doing so could lead to breaches in other treaty commitments, notably involving Nato, and would have serious practical implications, British officials said.

Pressure would be applied on the US not to use its cluster weapons in joint operations with countries which had banned them, officials suggested, but the government will not stop the US stockpiling cluster weapons at American bases in the UK.

Human rights groups that campaigned for a ban have also called for Brown to end the US stockpiling on cluster bombs in the UK.

"Gordon Brown has pushed the Dublin negotiations in the right direction. Now is the time for him to have the courage of his convictions and tell the US that it cannot store these outdated and indiscriminate weapons on UK soil," said Simon Conway, a former soldier and the director of Landmine Action UK.

But the Cluster Munition Coalition – co-chaired by Conway – hailed today's announcement of a British ban ahead of the treaty as "a major act of statesmanship" by Brown.

Labour peer Lord Dubs, a long-standing campaigner against the use of cluster weapons, said he was "delighted" by Brown's comments, which he said should open the door to "a proper, robust convention".

Article one of the planned treaty, due to be signed in Oslo in early December, prohibits assistance with the use, transfer and stockpiling of cluster munitions. The US, Israel, Russia, China, India and Pakistan are not taking part in the talks.